Photographic fixative composition



Patented Apr. 2, 1940 UNITED STATES PATENT OFFICE PHOTOGRAPHIC FIXATIVECOMPOSITION Merlin Martin Brubaker, Wilmington, DeL, assignor toDu PontFilm Manufacturing Corporation, New York, N. Y., a corporation ofDelaware No Drawing. Application October 11, 1938, Serial No. 234,481

17 Claims.

. ing. A still further object is the provision of an acid hardeningfixing composition which may be used for the preparation of photographicfixing baths. A still further object is the preparation of an acidhardening fixing bath which has a long life. A still further object isthe preparation of an acid hardening fixing bath which will maintainsatisfactory hardening over a Wide range of 7 pH values. A still furtherobject is the preparation of an acid hardening fixing bath which is freefrom sludging tendencies and has a low rate of sulfurization. Otherobjects include, new processes of fixing photographic film and a generaladvancement of the art. Still other objects will be apparent from thehereafter described invention.

The above and other objects are accomplished by the incorporation of thesulfamic acids or their easily hydrolyzable salts in afixativecomposition. In a more limited sense, they are accomplished by theincorporation of the sulfamic acids or their easily hydrolyzable saltsas an acid constituent indry photographic fixing compositions,concentrated photographic fixing solutions and in photographic fixingbaths. In a preferred embodiment of the invention they are accomplishedby the use of sulfamic acid in dry photographic fixing compositions,concentrated fixing solutions and in photographic fixing baths. l

Photographic fixing baths contain at least three basic ingredients, viz:(1) a silver salt solvent or fixative salt such as sodium thiosulfate,potassium thiosulfate, ammonium thiosulfate and their hydrationproducts, e. g. hypo; (2) an acid to neutralize the alkali of thedeveloper carried over into the fixing bath by the photographi element;and (3) a soluble sulfite to inhibit the d composition of the fixativesalt. Such baths are known as acid fixing baths. Photographic fixingbaths usually containa fourth asic ingredient, namely, a hardening agentfor t eernulsion binder which is usually composed of gelatin, e. g.potassium alum, chrome alum, etc. The last mentioned baths are known asacid hardening fixing baths.

The useful life of an acid hardening fixing bath is usually terminatedby any one of three events: (1) exhaustion of the fixing agent withconsequent excessive clearing; time for the emulsion layers, (2)sulfurization, rendering the bath unfit for use, and (3) sludging fromexcess alkalinity, usually caused by the carrying over of developer fromthe developer bath by the films, plates or papers processed.

1 It has been found that the sulfamic acids and substances which readilyyield sulfamic acid by hydrolysis in aqueous photographic baths may beused as the acid ingredient of acid fixing and acid hardening fixingcompositions, baths and concentrated solutions. These acids areadmirably suited for the purpose and maintain the pH of the resultingbath under optimum conditions in that they inhibit sulfurization andsludging and furthermore render the hardening agent effective over awide pH range.

It has-also been found that the water-soluble salts of the sulfamicacids also have a beneficial effect in the above-described baths andcompositions. Aqueous photographic baths contain in addition to theinitially added ingredients the reaction products of the ingredients. Inthe case of the sulfamic acids, the water-soluble salts are formed inthe bath during use. For instance, if sodium sulfite is used in the bathcontaining sulfamic acid, sodium sulfamate is formed. Because of thebeneficial effect of the salts, it is preferable that they be addedinitially. Among the beneficial effects are the facts that the saltshave a buffering action and certain salts have a hard.- ening efiectupon the proteins.

The invention will be further illustrated but is not intended to belimited by the following examples:

nxmm 1 Sodium thiosulfate, 7H2O' grams 240 Sodium sulfite, anhydrous do15 sulfamic acid do Boric acid d0 7.5 Potassium alum do 15 Water toliters 1 2,195,406 Similar results may be obtained with the fol- Mia: Blowing fixing baths: Grams EXAMPLE 2 Potassium alum 32 Sodiumthiosulfate, 71120 grams 350 sulfemm 11 Sodium sulfite, anhydrous do 15To prepare the working bath, Mix A is dis- Sulfamic acid do 10 solved in600 ccs. of hot water. When cooled, Boric acid do 40 Mix B is added withconstant stirring and when Potassium alum do 32 dissolved, the finalvolume is brought to 1 liter Water to liters 1 with cold water.

EXAMPLE 3 EXAMPLE 8 Sodium thiosulfate, 'ZHzO grams 350 Mm A Sodiumsulfite, anhydrous do 15 Grams Sodium citrate 30 Sodium thiosulfate,anhydrous 350 Borax 10 Sodium sulfite, anhydrous 15 Sulfamic acid 10Sodium acetate, crystals 30 Potassium alum do 32 3 Water to liters 1Grams EXAMPLE Potassium sulfamate 30 Sodium thiosulfate, 71-120 grams350 sodium t anhydrous 18 For pr mg a ry p w ph phw fi sodium acetate 13tive composition, Mix B is contained in a small Sulfa i 3 m 10 cartonwithin the large bulk, Mix A, which can Boric acid then be stored untilrequired. For use, Mix A Potassium alum 32 is dissolved in 750 ccs. ofhot water and then Water to m; 1 the contents of the inner carton, Mix13, are

added with constant stirring. When all ingre- EXAMPLE 5 clients aredissolved, the final volumeis brought Sodium thiosulfate, crystals-grams 350 to 1 hter cold water- Sodium sulfite, anhydrous do 15 EXAMPLE9 Potassium tartrate do 30 Sulfami acid L 8 Sodium thiosulfate, crystalsg rams- 300 Potassium alum 30 Sodium sulfite, anhydrous do 15 Water to"liters" 1 Glycol bori-borate do 10 N-methylol sulfamate do 30 Th s bathshowed excellent resistancetowards Sulfamic acid, 5 sludgmg andsulfurization. water o "liters" 1 I The Sulfamic acids lend themselvesremarkably wellto the preparation of dry powder mixtures comprising theactive ingredients or fixing baths.

These photographic fixative compositions when dissolved in water, yieldacid fixing baths having exceptional long fixation life and areresistant to sludging and sulfurization. The following examplesrepresent dry powder which, when dissolved in water yields ready-to-usefixing baths. If a hardening fixing bath is desired, alums can be addedafter the bulk of other ingredients are dissolved.

ExAmLE 6 Grams Sodium thiosulfate, anhydrous 225 Sodium sulfite 15Sulfamic acid 1-0 Sodium citrate 30 Boric acid 10 Dissolve in '750 ccs.of hot water, then add 32 grams of potassium alum with constant stirringand add cold water to make the final volume 1 li er.

EXAMPLE 7' A complete, dry powder fixative composition, comprising allthe necessary basic ingredients and requiring only to be dissolved in agiven amount of water, which can be prepared in advance of use andstored over long periods of time,

An exposed and developed film when treated in the above bath fixedrapidly and completely and led to a clean negative. The bath furthermorehad good gelatin hardening properties.

EXAMPLE 10 Concentrated bath Due to its high solubility in water, incomparison with other dry acids suitable for fixing baths, sulfamic acidlends itself particularly well to the preparation of concentrated stocksolutions of fixing baths, a suitable formula being:

The sodium sulfite is first dissolved in 200 ccs.

EXAMPLE 11 Sodium thiosulfate, 7H2O grams 240 Sodium sulfite, anhydrousdo 6 Sulfamic acid 1 do 6 Aluminum sulfamate do 8 Water to liters 1 Thisbath in addition to its good fixing properties has, by reason of itsaluminum sulfamate content, an excellent tanning effect on the proteincarrier layers used in photographic emulsions.

v EXAMPLE 12 Sodium thiosulfate, 7H2O grams 350 Sodium sulfite,anhydrous do 15 Sodium citrate do 18 N-methyl sulfamic acid do 12Potassium alum do 32 Water to liters, 1 In place of the substitutedsulfamic acids and .ions, other acidic compounds which yield such ionsmay be used in place thereof or in admixture therewith. Asfurther-examples of suitable compounds, mention is made of sodiummetaborate, potassium tetrahydrodiborate, sodium hexahydrotetraborate aswell as other water soluble, particularly alkali metal salts of theoxygen acids of boron. The organic esters and salts of ester of theboron acids, e. g. glycol borate, lycery'l borate, glycol and glycerolboriborate, the aryl-boric acids, including phenyl boric,pcarboxylphenylboric, p-tolyl boric acids and their alkali metal andammonium salts are very effective when used. in combination with thesulfamic acids'and sulfamates of this invention.

, The addition of small quantities of other acids,

such as tartaric, fumaric, malic, maleic, lactic,

* glycolic, glycerophosphoric, propionic and butyric may be resorted to.The lithium, sodium, potassium salts of these acids, as well as any ofthe above acids may be used as a source of the acid ions. Thewater-soluble salts of the sulfamic acids herein described such as thesodium, potassium, lithium, ammonium, aluminum, etc. salts are veryuseful. It has been found that the sodium and potassium salts of thediand polybasic acids especially the organic acids, are particularlyeffective in fixing compositions and baths containing sulfamic acids ortheir substitution derivatives in causing the resulting baths to behighly resistant to sludging and sulfurization. These salts of citric,tartaric, boric, succinic, malic and, maleic acids which have 2 or 3ionizable sodium or potassium groups are more effective than 1 thoseacids which yield a single sodium or potassium ion such as sodiumacetate.

In place of the specific fixing salts set forth in the precedingexamples, any water soluble thiosulfate may be substituted. Suitablethiosulfates including ammonium thiosulfate, potassium thiosulfate,lithium thiosulfate, thiosulfate complexes such as potassium andmagnesium thiosulfate.

Fixing baths prepared according to the foregoing invention have a numberof distinct advantages. They have a long fixation. hardening and stainpreventing life. They are remarkably resistant to sulfurization andsludging and in the latter respect will tolerate exceedingly highconcentrations of alkali developers before showing tendencies to sludge.

The sulfamic acids and particularly sulfamic acid, are well suited fordry fixing powders and may be packaged and stored for long periods oftime.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodiments hereofexcept as defined in the appended claims.

I claim:

1. A composition containing a photographic fixing agent and at least onecompound taken from the group consisting of sulfamic acids, substanceswhich readily yield sulfamic acids by hydrolysis in aqueous baths andwater soluble salts of sulfamic acids.

2. A photographic fixative composition containing a photographic fixingagent and a sulfamic acid.

3. A composition containing a photographic fixing agent and sulfamicacid.

4. A photographic fixative composition comprising a soluble thiosulfateand a sulfamic acid.

5. A photographic fixativei composition comprising a solublethiosulfateand a sulfamic acid salt, and a sulfamic acid.

6. A photographic fixative composition comprising an alkali metalthiosulfate and sulfamic acid.

7. An acid hardening photographic fixing coniposition comprising analkali metal thiosulfate, sulfamic acid, a water soluble sulfite, and aprotein hardening agent.

8. An acid hardening photographic fixing composition comprising analkali metal thiosulfate, an alkali metal sulfite, sulfamic acid, aprotein hardening agent and a substance capable of yielding differentacid ions.

9. A dry photographic fixative composition solid substance is sodium 13.A photographic fixing composition comprising a concentrated aqueoussolution containing a water-soluble thio sulfate, a water solublesulflte, a sulfamic acid and a protein hardening agent.

14. An aqueous photographic fixing bath containing a fixing agent andsulfamic acid.

15. A photographic fixing bath comprising an alkali metal thiosulfate,an alkali metal sulfite, sulfamic acid, and a protein hardening agent.

10. The process which comprises fixing a photographic element in thepresence of a sulfamic acid.

1'7. The process which comprises fixing a photographic element in thepresence of sulfamic acid.

MERLIN MARTIN BRUBAKER.

